1. Field of the Invention
This invention is in the field of disposable dental floss holders and particularly injection molded devices, each formed integrally as a handle plus a bow across which a strand of dental floss is spanned, and in the field of manufacturing dental floss holders.
2. Related Inventions
This invention is related to disclosures in the following U.S. patents:
______________________________________ Pat. No. Inventor Date ______________________________________ 4,006,750 I. S. Chodorow 2-8-77 4,016,892 I. S. Chodorow 2-8-77 77244,376 I. S. Chodorow 5- D 250,214 D 251,075 N. Schiff 2-13-79 D 251,074 N. Schiff 2-13-79 D 301,071 R. Franchi 5-9-89 D 312,894 J. Schroder-Jorgensen 12-11-90 3,858,594 G. Ensminger 1-7-75 5,086,792 I. S. Chodorow 2-11-92 ______________________________________
3. Background and Prior Art
This invention is in the field of devices for personal and professional dental care, particularly for removing plaque from the teeth surfaces and food particles from between teeth.
For many years teeth have been cleaned primarily by manual or power-driven brushing, and the spaces between teeth have been cleaned by a variety of methods including brushing, machine-driven jets of water, toothpicks, and the like, and by flossing with the commonly available nylon dental floss and dental tape or similar thread or even rubber bands.
Until recently the most generally accepted objective in cleaning teeth was to remove food particles and chemicals, particularly sweets from tooth surfaces. However, now it has been established and is being taught by a growing number of dentists, orthodontists and periodontists, that the chief cause of caries (dental cavities) and a principal cause of periodontal (gum and root) disease is a bacterial plaque formation that develops on tooth surfaces. When removed, new plaque can reform in less than 24 hours. The causes of plaque development are not fully appreciated; however, a person's normal body chemistry independent of his particular diet, can be a contributing factor.
Plaque is the name given to a bacterial substance that begins as an invisible film of micro-organisms, and with saliva and foods, particularly sugars, forms a soft sticky white film on the surfaces of teeth and between teeth. If plaque is not removed daily it can develop and harden into a firmly attached substance called calculus or tartar which may cause gums to redden and swell in a condition known as gingivitis. This disease is often characterized by receding gums which causes the creation of small pockets around the teeth which trap food particles and bacteria. These pockets can enlarge if the gums become further inflamed or infected causing the bone supporting the teeth to become infected and destroyed. The weakened tissue is infection-prone and once so injured the gums cannot protect the underlying bone from the spread of this disease. Additionally, bacterial plaque produces noxious chemicals which cause cavities and irritate the gums. This is the manner in which teeth become loosened and ultimately lost, the latter stages here-described being periodontal disease.
Of the methods mentioned above for cleaning teeth, brushing is not effective to remove plaque from interdental tooth surfaces between the teeth. Water jets are not sufficiently abrasive to achieve plaque removal, though they may remove food particles very well. Also, toothpicks are too thick and cumbersome to probe and scrape between two closely adjacent surfaces. This leaves only dental floss, typically a strand of multi-filamented nylon that is moved in a reciprocating action into the crack or space between the sides of two teeth. The unwaxed version of dental floss is less smooth and thus more abrasive and more effective in scraping plaque off the tooth enamel surfaces in question. However, the user of any floss has the problem of maneuvering it-while under certain tension, down between each pair of teeth, including the rear-most teeth. Positioning floss is inconvenient in most teeth locations, quite difficult in many, and almost impossible in others. The procedure generally includes winding opposite ends of a strand around one finger of each hand respectively, then inserting these two fingers of both hands into the mouth, attempting to position the span of floss between the fingers in the desired location, and finally reciprocating the floss between teeth while also moving it vertically along the tooth from tip to gum. The floss is maneuvered preferably just under the edge of the gum, held firmly against and wrapped partially around the proximal surface of the tooth and pulled over its surface toward the chewing edge.
It is known from surveys that most people, even including those who take seriously the matter of dental care and brushing regularly, do not use floss daily because the technique for use as described above is so tedious. For a number of years there have been attempts to render flossing less tedious and also to render it more effective by the development of holders onto which floss is attached. Most holders have two arms across which the floss is strung; however, secondary complications described below with the holders themselves have resulted in general non-use, and thus there has been no remedy to the original problem of non-use regularly of floss held by hand.
One basic problem with the holders is that floss stretches, eventually frays, becomes thin, and breaks when used. Whether the floss holds up for five, twenty or more teeth depends upon the tightness of the interdental spaces and the abrasion the floss incurs. By the original manual operation before floss holders, the floss user merely pulled the exposed end of floss from a spool, cut off a segment and then wound the cut segment on his or her fingers. With certain floss holder devices the user must, for each flossing operation, obtain a length of floss, thread or carefully position it about a floss holder, pull on some part of the floss until it is in tension, and finally secure it under tension to the holder. Whether a floss supply is provided on a spool in the holder handle according to one device, or provided from a separate spool from which segments of floss are cut as needed, the remaining threading and tensioning procedure is still an inconvenient burden.
From these manually strung or manually loaded flossing devices there developed pre-strung disposable flossers where a strand of floss of length to span the bow or spaced arms of the flosser had its ends secured to the arms in situ, namely at the same time the flosser handle and arms were injection molded. These devices have gained wide popularity and sales because they are convenient to use and to carry, and because they can be mass produced and sold at very low per unit cost.
Samples of prior art flossers of the type with an injection molded handle and floss pre-strung at the time of molding, and disclosures of known manufacturing methods may be seen in U.S. Pat. Nos. 4,006,750, 4,016,892, 5,086,792 and in the other patents cited above which are hereby incorporated herein by reference. These and similar devices, regardless of the geometric configuration of the handle, have certain useful features in common and certain troublesome features in common. On the positive side are the light weight and inexpensive holders, each with a bow portion formed by spaced arms and a segment of floss spanning the bow. Some configurations, i.e. with floss parallel to the handle, may be more convenient than others for particular users.
On the negative side, applying to all prior art disposable flossers with a permanently prestrung bow portion, are the following points. A typical user of a dental floss holder (flosser) would like to use a single flosser or as few flossers as possible to clean between all the teeth in his/her mouth. Thus, the floss spanning the bow of the flosser will be inserted repeatedly between different adjacent teeth. If the floss is multifilament type and if at least some of the teeth are closely or tightly adjacent, the floss in the flosser becomes stretched and/or becomes frayed and may even break. Monofilament floss tends less to stretch, fray or break; however, it is less abrasive than multifilament floss and accordingly is less effective in removing plaque, and thus is less desirable for many floss users.
Tensioning of the floss occurs each time the floss strand is urged to pass into the interspace between two closely or tightly adjacent teeth. After one or more tensioning uses of a strand of floss in a holder it will stretch and then have slack and no longer be taut and linear between the arms or ends of the bow. Consequently, the next time the flosser with slack floss is used to penetrate the interspace between two teeth the floss takes a deep generally V-shaped configuration as penetration of the interspace is begun. This leads to two undesirable consequences. First, since the floss is not taut the bow must be moved further toward the gums than if the floss were taut. When the floss pops through the interspace the bow ends may be positioned below the gum line, so the floss will pop through trying to reach a neutral condition and strike the gum, which is highly undesirable as it can cut, bruise or otherwise harm the gum.
Another reason why some prior art pre-strung flossers develop slack floss is because one or both floss ends slip slightly out of an arm of the bow during tensioning as the flosser is used. Slippage occurs when the floss is not well bonded to the holder which may occur because the plastics are incompatible or because the floss and the injection molded plastic are not heated and cooled uniformly or at least not at appropriate respective temperatures and time periods for secure bonding together.
In conclusion, floss often stretches and subsequent attempts to use a flosser with stretched floss present difficulties or undesirable situations for the user. If the floss ends are well-anchored in the bow arms, stretching still occurs. If the floss ends are not well anchored the floss slips and slack results. Either way, after a few penetrations of interspaces many flossers have lost their tension of the floss.
In the new invention we have identified a problem and discovered a solution in the form of a new device and a new method of manufacturing these devices, as set forth below.